Propeller pitch reversing control switch



J. BORDELON March 26, 1957 2,786,916

' PROPELLER PITCH REVERSING CONTROL SWITCH Filed Spt. 22, 1953 2 She ets-Sheet 1 IIIIIN INVENTOR: Lawrence J. florde/on United States Patent PROPELLER PITCH REVERSING CONTROL SWITCH Lawrence J. Bordelon, La Mesa, Califl, assignor, by mesne assignments, to General Dynamics Corporation, a corporation of Delaware Application September 22, 1953, Serial No. 381,627

6 Claims. (Cl. 200--87) This invention relates generally to electric circuit controlling instrumentalities and more specifically to an electric switch construction having particular use in connection with the control of hydraulically actuable controllable pitch propellers. The present invention constitutes an improvement of propeller pitch reversing control switches of the type shown in my patent, No. 2,579,172, issued December 18, 1951.

An object of the present invention is to provide an improved switching mechanism embodying a unique arrangement of circuit making and breaking elements.

A further object of the present invention is the provision of an electrical control instrumentality of novel construction which is adapted for actuation and control by the usual engine throttle lever.

It is yet another object of the present invention to provide an improved form of switching mechanism which embodies electrically associated switch units which are adapted for operation by a common actuating means.

A further object of the invention is the provision of a simple, compact, and reliable switching mechanism for effecting controlled reversing and unreversing operation of a propeller blade.

Another object of the present invention is to provide a novel switching mechanism for controlling controllable pitch propellers, which switching mechanism embodies safety means to substantially prevent accidental pitch reversing of a propeller.

Other objects and features of the present invention will be readily apparent to those skilled in the art from the following specification and appended drawings wherein is illustrated a preferred form of the invention, and in which:

Fig. l is a perspective view of a switching mechanism in accordance with the present invention, portions of the mechanism being cut away for clarity;

Fig. 2 is a side elevational view, partially in section, of the switching mechanism, the side plate having been removed for clarity;

Fig. 3 is a side elevational view, partially in section, of the switching mechanism, portions of the mechanism being cut away for clarity;

Fig. 4 is an end elevational view, partially in section, of the switching mechanism;

Fig. 5 is a detail vertical sectional view of one of the snap switch units of the switching mechanism;

Fig. 6 is a detail vertical sectional view of another of the snap switch units of the switching mechanism;

Fig. 7 is a digrammatic view showing a hydraulically actuated controllable pitch propeller and a pitch reversing control system associated therewith;

Fig. 8 is a schematic diagrammatic illustration of the switching mechanism showing the normal relative positions of the various operating elements;

Fig. 9 is a view similar to Fig. 8 but with the operating elements illustrated in the relative positions assumed when reversing of the propeller pitch is being accomplished;

Fig. 10 is a view similar to Fig. 8 but with the operating Patented Mar. 26, 1957 elements illustrated in the relative positions assumed when unreversing of the propeller is being accomplished;

Fig. 11 is a view similar to Fig. 8 but with the operating elements illustrated in the relative positions assumed during resetting of the switching mechanism; and

Fig. 12 is a schematic wiring diagram of the reverse pitch control circuit shown in association with the feathering control wiring circuit for the propeller.

Particular reference is now directed first to Fig. 7, wherein the electric circuit controlling instrumentality of the present invention is shown incorported in a system for effecting control of a propeller. This system, as illustrated, embodies an aircraft power plant comprising an internal combustion engine, generally indicated at 10, which engine 10 is equipped with a hydraulically actuable controllable pitch propeller 11. Propeller 11 has a propeller hub 12 to which are movably secured a plurality of propeller blades 13 adaptedto rotate about their longitudinal axes to change their pitch angle or angle of attack. Suitable hydraulic pitch changing mechanism, indicated generally at 14, is contained within a dome 15 and includes a piston 16 reciprocable in a cylinder 17. Piston 16 is made to move within its containing cylinder 17 by the force exerted by hydraulic fluid supplied under pres sure to the opposite ends of the cylinder 17. Piston 16 is suitably operatively connected to the propeller blades 13 through a rotatable member 18 carrying gear means 19 which are adapted to mesh with usual beveled gear means (not shown) provided on the inner or base ends of the propeller blades 13. The piston 16 is joined to the rotatable member 18 through a usual cam follower-cam track arrangement 26 for effecting rotation of member 18 upon reciprocating movement of the piston 16. This organization of elements acts to convert reciprocable movement of piston 16 into rotative, pitch changing movement of the propeller blades 13. For a more detailed description of the arrangement of the propeller blades and the operative connection thereto of the actuating mechanism, reference may be had to United States Patent No. 2,361,- 954, issued November 7, 1944, for Propeller Control Means.

A suitable governor 21 conveniently mounted on the engine 1%) acts to supply fluid to pitch changing mechanism 14 to automatically effect adjustments in propeller blade pitch necessary to maintain constant engine speed under varying flight conditions. The fluid provided by the governor 21 to the pitch changing mechanism 14 for automatic operation of the latter is taken, as is normal, from the usual engine lubricating system through a conduit (not shown). A conduit 22 connects the governor 21 to the space at the pitch reducing end of piston 16 while a second conduit 23 permits fluid to be passed to the space at the pitch increasing side of piston 16. Oil will be directed to either side of the piston 16 by the governor 21 as required by flight conditions. During an underspeed condition of the engine the governor 21 is adapted to operate to pass oil through conduit 22 to the inboard side of piston 16 to provide pressure to cause the propeller blades 13 to move to a lower pitch whereupon engine speed increases. With an overspeed condition the governor 21 will respond to direct oil through conduit 23 to the outboard side of piston 16 to cause propeller blades 13 to move to a higher pitch, thereby decreasing the engine speed. The particular construction of the governor 21, it is understood, forms no part of the present invention as it is contemplated that such usual governors may be employed as are adapted, in response to external conditions, to cause fluid to be passed to one or the other of the two conduits 22 and struction as fully described in a manual entitled Propeller Hydromatic Governors No. 123, published by Hamilton Standard Propellers of East Hartford, Connecticut. Associated with governor 21 and the controllable pitch propeller 12 is a control system, indicated generally by the numeral 25, which is adapted to accomplish movement of the propeller blades 13 from their normal range to their reverse pitch positions. Positioning of the propeller blades 13 in reverse pitch serves a primary desirable function reducins airplane landing runs. The attainment of this condition must be rapid. efficient and certain and the control system 25 herein described reliably provides the desired result.

The control system 25, as shown, includes a suitable gear type pump 26 driven by an electric motor 27. It is here noted that pump 26 used in the reversing operation serves also in effecting the feathering operation, so the reversing operation does not require its own separate pump. A fluid line connects the inlet of pump 26 with the sump of an oil tank 31 which may be the source of supply for the engine lubrication system. The pump 26 is connected through a conduit 32 to the governor 21 whereby auxiliary oil is supplied to the governor 21 to supplement the normal oil output of the 'ovcrnor, which supplemented oil output is directed by the governor to the pitch control mechanism 14 for use thereby during feathering, unfeathering, reversing and unreversing operations of the propeller blades 13.

Associated with the governor 2 and adapted to affect the oil supplying operations thereof are a solenoid valve member 33 a pressure switch 3 The solenoid valve 33 is of a suitable construction adapting it to direct the flow of high pressure auxiliary oil from conduit 32 so that it, in a manner well known in the art, supplements the pressure of the normal oil provided by the governor 21 on either the inboard or the outboard side of the piston 16 as required to change the angle of the propeller blades 13. The pressure switch 34 is provided to stop the operation of the pump 26 in usual manner when the oil pressure in propeller cylinder 17 builds up to a predetermined value, as in the feathering operation. The pressure switch 34 is operatively connected to the propeller governor 21 so that the oil pressure difierential across the propeller piston 16 is duplicated in the pressure switch 34. Thus when the oil pressure in cylinder 17 builds up to the cut-out value of switch 3 after the completion of a propeller feathering operation the switch breaks the electrical circuit to the motor 27 of pump 26, in a manner and through the use of various mechanisms to be hereinafter described in detail. to thereby close off the auxiliary pressure being provided to the piston 16 and return the pitch changing mechanism to the normal control of governor 21.

A pump relay 35, of conventional construction and electrically connected to the electric motor 27 through a conductor 36, directly controls the flow of current to the motor 27 for energization and deenergization thereof.

Positioned on a propeller blade 13 is a cam ring 37 of usual construction electrically associated with a ground switch 38, as will be described. The ground switch 33 in turn is connected to an electrical circuit controlling instrumentality or switching mechanism 39 which is constructed in accordance with the present invention, and the details of which will hereinafter be fully described.

The cam ring 37 together with ground switch 38 and control switch 39 serves to disrupt the current supply to pump relay 35 to dcenergize pump motor 27 to shut off the flow of auxiliary oil from pump 26 when the propeller blades 13 have returned to positive pitch after an unrevcrsiug operation has occurred. This operation will be described in greater detail hereinafter.

A battery 41, or any other primary current supply source, is provided to supply the power for use in the operation of the control system 25.

he propeller reversing control switch 39 constitutes the primary reversing and unreversing control member in the control system 25 in that it controls the flow of current from the battery 41 into the system. The solenoid valve 33, pump relay 35, ground switch 38 and battery 41 are all electrically connected to the propeller reversing control switch 39 respectively through conductors 42 and 43, 44, 45, and 46. The exact operation of switch 39 and its control of the devices associated therewith will be described in complete detail later.

To effect reversing of propeller 11 the propeller reversing control switch 39 must be actuated. A preferred manner of securing actuation of the switch 39 is through a suitable manually operated throttle control lever 47 wiich as illustrated in the drawings is provided with an arcuate cam surface 48 adapted to engage with and operate the switch 39. The throttle lever 47 is utilized for operation of the switch 39 since it is a control member conveniently located for easy reach by the operator. It is to be understood that the particular construction of throttle control lever 47 forms no part of this invention, as the invention contemplates the use of any usual engine throttle which can be associated with the propeller reversing control switch 39 in a manner to permit the manual force applied to the throttle to be transmitted to the switch 39 to actuate the latter.

Referring now to Figs. 1 through 4 inclusive, the construction of the electrical instrumentality, switching mechanism, or propeller reversing control switch 39 is therein illustrated and as shown comprises a metallic casing or housing 49, formed with its top, bottom, and one side open and having end walls 51 and 52 and a side wall 53. To effect a substantially closed structure the top is partially closed and the bottom is completely closed by suitable top and bottom cover plates 54- and 55, respectively, and a side plate 56 is fitted across the open side of housing 49. Suitable studs or screws 57 threaded into end wall 51 and side wall 53 secure top cover plate 54 in place, and suitable studs or screws threaded into end walls 5.1 and 52 secure bottom cover plate 55 in place. In addition, side plate 56 is secured in position by usual studs or screws 58.

Integral with side wall 51 are a pair of spaced ears or tabs 59 mounted to the lower portion of end wall 51, as illustrated. Similarly, a pair of spaced ears or tabs 61 are integrally mounted to the upper portion of end Wall 52. Tabs 59 and 61 each embody a central hole to thereby facilitate the mounting of control switch 39 to any suitable support structure (not shown).

Fitted across the side of housing 49 which is closed by side plate 56 and located inwardly of this side plate 56 is a support plate 62, best illustrated in Figs. 1 and a 4. Plate 62 is rigidly secured to end walls 51 and 52 by a pair of suitable studs or screws (not shown) which are disposed through threaded holes 63 and 64, respectively, walls 51 and 52 being cut away or recessed sufiiciently, as at 65, Fig. 1, to accommodate plate 62 and afford a flush surface for side plate 56. As will be described in further detail hereinafter, support plate 62 serves as a mounting member for certain of the components of control switch 39.

Reference now will be had to Figs. 5 through 12 inclusive, wherein is illustrated a pair of usual unitary switch units 66 and 67 of the snap-acting type, each of which are located within the upper portion of housing 49 and secured therewithin in a manner to be described.

Switch unit 66, best illustrated in Fig. 5, includes an upper contact 68 and a lower contact 69, located in spaced relationship, and a movable contact carrying or switching member 71 operable between these contacts but being biased toward and into engagement with one of the contacts, which here is the upper contact 63.

Switch unit 67, best illustrated in Fig. 6, includes a single upper stop element '72, made of insulating material, a pair of adjacent, laterally spaced, lower contacts 73 and 74, and a movable contact carrying or switching member operable between stop element 72 and the pair of contacts 73 and 74 therebelow, but normally lor cated in engagement with element 72.

Mounted within the upper left hand portion of hous ing 49 by suitable bolts or screws 70 threaded into end wall 51 is a third unitary switch unit 76 of the snap-'act ing type. Unit 76 is essentially similar in construction to unitary switch unit 66 and therefore its construction is not shown in detail. However, it is diagrammatically illustrated in Fig. 8 and there it is indicated as including an upper contact 77 and a lower contact 78 in spaced relationship and a movable contact carrying or switching member 79 operable between these contacts but being biased toward and into engagement with the upper contact 77.

It is understood that the particular construction of switch units 66, 67 and 76 does not form a part of this invention. These switch units are of the general type described and claimed in U. S. Patent No. 1,960,020 to P. K. McGall, each embodying a contact arm or leaf spring means supported at one end in cantilever fashion, the other end being free to move. This leaf spring means operates in combination with compressed spring means, the parts of the switch being so arranged that the free end of the leaf spring means will move with a snap action when pressure is applied to it adjacent its supported end, all as is well known to those skilled in the art, and as is particularly pointed out and described in the aforesaid U. S. Patent No. 1,960,020.

For actuation of the snap-acting movable contact carrying members 71 and 79 of switch units 66 and 76 out of engagement with their associated upper contacts 68 and 77 and downwardly into circuit making engagement with lower or opposed contacts 68 and 73, respectively, units 66 and '76 are provided with upwardly biased operating pins 01 and 82, respectively, which pins project upwardly from the switch enclosings and are each adapted to be depressed to provide the operating force for displacing their associated movable contact carrying members. Upon depression of pin 81 or pin 82, as the case may be, the associated movable contact member will be moved downwardly with a snap action motion into circuit making engagement with the opposed contact, and immediately upon release of the downwardly operating force which is acting upon the pin, the movable contact member will automatically snap back into engagement with the other or upper contact.

For actuation in switch unit 67 of the snap-acting movable contact carrying 75 out of engagement with stop element 72 and into circuit making engagement with lower contacts 73 and 74, there is provided an upwardly biased upper operating pin 83 which projects upwardly from the switch enclosing and is adapted to be depressed to provide the operating force which effects movement of movable contact member 75. Upon depression of pin 83, the movable contact member 75 will be moved downwardly with a snap action motion into circuit making engagement with contacts 73 and 74. It is here noted that contact member 75 is so arranged that it remains in engagement with contacts 73 and 74 after release of the downwardly operating force which depressed pin 63 to actuate member 75. Thus it is seen that switch unit 67 is substantially similar to the switch embodiment described in U. S. Patent No. 1,960,020 at page 3, lines 7 through 14. More specifically, the contacts 73 and '74 of switch unit 67 are below the dead center position of switching member 75, and after switching member 7 has been urged overcenter and into engagement with contacts 73 and 74 switching member 75 does not return to its initial engagement with upper element 72 until urged thereagainst with the outside aid of a lower reset or operating pin 04, which pin projects downwardly from the switch enclosing and is adapted to be moved upwardly. Upon the application of force to effect upward movement of lower pin 34 contact member 75 will be reset or moved upwardly with a snap action into engagement with upper stop element 72, where member 75 will remain until again acted upon by upper pin 83. Thus, switch unit 67 difiers from switch units 66 and 76 in that its movable contact carrying member 75 requires an external actuating force to be applied in each of its movements. Contact carrying members 71 and 79 of units 66 and 76 require an external force to move them from a normal position and automatically return to their normal position immediately upon withdrawal of the external force.

To individually actuate the operating pins 81, 82 and 83 of switch units 66, 76 and 67, respectively, there is mounted to the upper portion of housing 49 an actuating mechanism or assembly, designated generally as 85, as illustrated in Figs. 1 through 4 inclusive. Assembly 85 comprises, generally, a pair of actuating arms 86 and S7 pivotally mounted within a pair of U-shaped mounting brackets 83 and 89, respectively, arm 86 being provided with a pair of pin actuator assemblies 91 and 92 for actuating pins 82 and 83 of switch units '76 and 67, respectively, and arm 87 being provided with a pin actuator assembly 93 for actuating pin 81 of switch unit 66. In addition, arms 86 and 87 are provided with a common roller 94 which is adapted to be engaged by cam surface 48 of throttle control lever 4-7 to effect pivotal movement, in a counter-clockwise direction, of arms 86 and 87 toward housing 49.

Arms 86 and 87 at their left end portions each, as viewed in the drawings, include a flat tongue or extension to which a plate 95 is rigidly secured, as by rivets 96, to thereby rigidly secure together the arms and also provide a mounting surface for a U-shaped bracket 97. Bracket 97, which carries roller 94, is fixedly attached to plate 95 by suitable fastening means, such as rivets 98, roller 94 being rotatably mounted upon a shaft 99 which is secured, as illustrated, between the upwardly extending side portions of bracket 97. With this arrangement of components, any displacement of roller 94 by cam surface 49 of throttle control lever 47 will result in a corresponding and common movement of arms 86 and 87.

To the right of their free end portions, arms 86 and 87, as illustrated, are generally channel shaped in cross section, and fit or nest above switch units 67 and 66, and within the pair of channel shaped mounting brackets 88 and 89, respectively. The downwardly depending channel or side portions of brackets 88 and 89, in turn, nest or fit against the outer side portions of a pair of U-shaped protective covers 101 and 102 which fit over and are coextensive with the top and side portions of switch units 67 and 66, respectively.

Support plate 62, switch units 66 and 67, protective covers 102 and 101, and mounting brackets 89 and 88 are each provided with suitable horizontally aligned openings through which a pair of comparatively long bolts or screws 103 are disposed, screws 103 being threaded into suitable threaded holes provided in side wall 53 to thereby securely fasten and support these components in position.

A pair of cylindrical spacers or bushings 10s and 105 are rigidly secured between the downwardly depending side portions of arms 86 and 67, respectively, at the right ends thereof, and a pair of pins 106 and 107 are slidably positioned through bushings 104 and 105 and the side portions of arms 86 and 87, and rigidly secured to the side portions of mounting brackets 38 and 89, respectively, thereby permitting pivotal movement of arms 36 and 87 and bushings 104 and 105 about pins 106 and 107. In addition, arms 86 and 87 are upwardly biased by a pair of coil springs 108 and 109 which are coiled about bushings 104 and 105, respectively. One end of each of springs 108 and 109 bears against the underside of one of corresponding actuating arms 86 and 87, and the other end of the springs bears against the upper surface of one of corresponding protective covers 101 and 102 thereby tending to urge arms 86 and 87 upwardly away from housing 49. Thus, when roller 94 is engaged by cam surface 48 of throttle control lever 47 the resulting counter-clockwise pivotal movement of arms 86 and 87 is against the bias of springs 16S and 189, respectively, and when roller 94 becomes disengaged from cam surface 48 the bias of spring 108 and 109 will urge arms 36 and 57, respectively, in a clockwise pivotal movement to the normally upward position, as illustrated in Figs. 1 through inclusive.

Pin actuator assembly 91, best illustrated in Pig. 3, serves to actuate pin 82 of switch unit 76 and is mounted upon plate 95, being disposed through suitable openings provided in plate and the left end portion of arm 86. Assembly 1 comprises a plunger member 111 which slidably extends through plate 9", arm 86, and is threadably connected at its upper end portion to a cylindri sl adjusting member 112. At its lower end, plunger member 111 embodies a larger diameter flat end portion 113 which is adapted for depressing a leaf spring element 114 upon counter-clockwise pivotal movement of arms 86 and 87, a suitable opening 115 being provided in top cover plate 54 for the passage of portion 113 therethrough for such depression. Spring element 11-; is located spaced above switch unit 76, one end of the spring element being suitably fixed in position, as at 115 as shown in Fig. l, and the other end thereof being positionet above actuating pin 82 of switch unit 76 whereby when portion 113 of plunger member 111 depresses spring element 114, actuating pin 82 is also depressed or actuated.

At its upper end, plunger member 111 is threadably connected as stated to adjusting member 112 which embodies an integral nut or stop portion 117. As illustrated, portion 117 abuts the upper surface of plate 95, and serves to adjust the distance of flat end portion 113 below plate to thereby adjust the time interval between the initial pivotal movement of arms 86 and 87 and the depression of: pin 32. Adjustment of this distance is made by rotation of nut portion 117 on the upper threaded end of plunger member 111, rotation one vay serving to shorten the distance, and rotation the other way serving to lengthen the distance, as is evident. A cotter key 113 disposed through suitable openings in plunger member 111 a d adjusting member 112 serves to maintain desire setting. A spring 119 disposed about the periphery of plunger member 111 between arms 86 and 27 and flat end portion 113 biases portion 113 downwardly thereby providing an override for plunger member 111 upon pivotal movement of arms 86 and 87 and contact of portion 113 with leaf spring element 11%. it is evident that the force causing pivotal movement of the arms is normally not fully exerted against pin 82 of switch unit 76 during contact of portion 113 and elem nt 114 because of the spring action provided by spring 119.

Pin actuating assembly 92, which serves to actuate pin 83 of switch unit 67, is mounted at approximately the mid portion of arm 86, as illustrated, through a suitable opening provided therefor in arm 36. Assembly 92 is identical to the previously described assembly 91, and embodies a similar plunger member, adjusting fitting, cotter key, and spring. The fiat end portion of the plunger member is adapted to pass through a suitable opening provided therefor in protective cover 101, and depress pin 83 of switch unit 67 upon counter-clockwise pivotal movement of arms and The adjustment of the interval before contact of the plunger member with pin 83 is made such that pin 83 is the last pin depressed of the pins 81, S2 and $3 to thereby close the contacts of switch units 76 and 66 prior to the closing of the contacts of switch unit 67 whereby arcing between the contacts of the various switch units is greatly reduced, as will be further explained.

Pin actuating assembly 93, which serves to actuate pin 81 of switch unit 66, is mounted at the right end portion of arm 87, as illustrated, through suitable openings provided therefor in mounting bracket 89 and arm 87. Assembly 93 is identical to the previously described assembly 91, and embodies a similar plunger member, adjusting, fitting cotter key, and spring. The fiat end portion of the plunger member is adapted to pass through a suitable opening provided therefor in protective cover 102 and depress pin 81 of switch unit 66 upon counterclockwise pivotal movement of rrms 36 and 87.

Disposed within housing 49 below switch unit 67 and in vertical alignment with lower or reset pin 84- of unit 67 is an electromagnet or solenoid 121. The rearward side of solenoid 121 fits within a mating depression 122 which is cut or machined out of side wall 53 to thereby aid in the desired positioning the solenoid. in addition, a holding bracket 123, disposed about solenoid 121 and fixed to side wall 53 by a pair of screws 12 i, rigidly secures solenoid 121 within depression 122 and in alignment with lower pin 84.

Solenoid 121 is of conventional construction and comprises a usual energizin" winding and a vertically movable armature or core 125. Core 125, upon energization of the solenoid, moves upwardly to thereby urge pin 84 upwardly whereby switch unit 67 may be reset, as previously described.

To afiord points of attachment for outside wiring leads to control switch there is provided a pair of threaded male plugs 12:; and 127 rigidly secured to end walls 51 and 52 of housing %9 by suitable fastening means, such as by a plurality of bolts or screws and 125 respectively, plugs 126 and 127' being insulated from housing 49 by usual insulation 131 and 132, respectively. Plug 126 embodies four pin contacts 133 while plug 127 em bodies a single pin contact 134- which serves to connect the lead which suppl'es power to the solenoid valve 33. To prevent inadvertent of the power circuit of control switch 39 and short-circuiting thereof or other undesirable occurrences care is taken to isolate the power wiring as much as possible. For this reason, further insulation for the internal lead attached to pin contact 134 is provided by a plastic insulating housing 135 which is rigidly secured to end wall 52 by the screws 129 and fits about the inner end of pin contact 134, housing 135 being suitably hollowed out to accommod-.te a lead. in addition, to prevent accidental grounding to housing 49 of wiring within housing 49, a thin layer of insulation 137 is suitably disposed against the inner surfaces of housing 4-9 as at end wall 52. and side wall 53; if desired, of course, similar insulation could be provided against the other interior walls although insulating of wells 52 an 53 only has been found to be sumcient.

Reference will now be ad to the wiring diagram of Fig. l2, which illustrates the incorporation of the reversing control system 25 with the feathering control system for the propeller 11. Combin ng the two systems permits the utilization by both control systems of certain of the same devices, such as the solenoid valve 33, relay 35. the electric motor driven pump 26, and the cam ring 37 of propeller blade 13.

Further provided to complete the feathering control system are a push-pull electric switch 133 and a double pole relay 139. Push-pull elec 'ic switch 133 embodies four pairs of opposed o itact .ncmbers, 141a and 1411'), 142a and 1-1-21), 143a 1a and 1440 and 14412. A bridging movable contact is disposed between the pairs of contact members for circuit-making cooperation with such contacts in groups of four comprised of one contact from each pair.

The ush-pull switch 133 also includes a manually operated actuator 146, an appropriately grounded warning light 147 associated with actuator 146, and a hold-in coil Actuator 1 36 is adapted to move bridging contact 145 in e ier direction from its normally contactsdisengaged position into circuit-making engagement with the various contact sets of push-pull switch 138. The light 147 serves to warn the operator when actuator 146 is in its depressed or in position, and hold-in coil 148 functions to maintain actuator 146 in such in position. Hold-in coil 148 is electrically connected at one end to contact 1431b and is connected at its other end by electrical lead 149 to ground through pressure switch 34.

The double pole relay 139 embodies a pair of switch arms 151 and 152 and an energizing coil 153 operatively connected to the switch arms 151 and 152 for movement thereof from their normally engaged contacts into circuit making engagement with opposed contacts. The double pole relay 139 and the push-pull switch 138 are electrically interconnected, coil 153 of relay 139 being connected at one end to contact 141a of switch 138 through a lead 154. The other end of coil 153 is joined by a lead 155 to a contact 156 of the propeller blade ground switch 38. Ground switch 38 includes a movable switch arm 157 which is actuated by a roller 16%) riding upon cam ring 37 to make or break electrical contact with contact 156 when propeller blade 13, and consequently cam ring 37, rotates to thereby make or break, respectively, a circuit from coil 153 to ground for purposes to be described.

Switch arm 151 of double pole relay 139 is connected through a lead 158 to solenoid valve 33, and its other switch arm 152 is connected through a lead 159 to solenoid valve 33 to thereby complete an electrical circuit from switch arm 151 through solenoid valve 33 to switch arm 152. Switch arm 151 on energization of coil 153 engages a grounded contact 161 of relay 139 while switch arm 152 on energization of coil 153 moves into engagement with a stationary contact 163 of relay 139 which connects through a lead 164 to contact 14211 of push-pull switch 138.

Direct current power to the push-pull switch 138 is provided through a lead 165 which connects to both contacts 144:: and 14% thereof. This power may be taken from any primary current source such as, for example, battery 41.

A coil 166 of pump relay 35 is connected at one end to ground and at the other end to both contacts 143a and 143b of push-pull switch 138 through a lead 167. On energization of coil 166 a movable contact 168 of pump relay 35 engages a pair of stationary contacts 169 of this relay 35 to thereby complete a circuit from a suitable power source through a lead 171 and a lead 172 to pump motor 27 and thence to ground through a lead 173.

The electrical connections from the various switch units 66, 67 and 76 and the solenoid 121 of propeller reversing control switch 39 to the various devices required to effect reversing of the propeller 11 will now be discussed.

A lead 174 interconnects battery 41 to movable contact 75 of switch unit 67 while one lower contact 73 of unit 67 is connected to coil 166 of pump relay 35 through a lead 175. The other lower contact 74 of unit 67 is connected through a lead 176 to movable contact arm 71 of adjacent switch unit 66.

Lower contact 69 of unit 66 is connected through lead 177 to a stationary contact 178 of double pole relay 139 which is normally closed in contact with switch arm 152 of relay 139.

Movable contact member 79 of switch unit 76 is connected to solenoid valve 33 through a lead 179, and lower contact 78 of unit 76 is grounded outside of reversing control switch 39 through a lead 181.

Solenoid 121 is electrically connected at one end to lower contact 74 of switch unit 67 through a lead 182, and is connected at its other end through an electrical lead 183 to contact 156 of propeller ground switch 38.

It is understood that push-pull switch 138 and double pole relay 139 do not enter into the control of the reversing and unreversing movements of the propeller 11. They are included merely to complete the feathering control system to illustrate that feathering control of propeller 11 and reversing control of propeller 11 each involve common use of a substantial number of control elements to avoid duplication of parts. i

Since the feathering of propeller 11 is incidental to. the present invention this operation will be described only briefly. To efiect feathering of propeller 11 the button of actuator 146 is depressed, closing a circuit to light 147 to thereby warn the operator that the feathering operation is in progress, actuator 146 also effecting the energization of coil 166 of relay 35 to close the circuit to motor 27 to start operation of pump 26. Hold-in coil 148 of push-pull electric switch 138 is also energized by current flowing therethrough to ground through pressure switch 34. Pump 26 supplies fluid to governor 21 to cause it to provide pressure to the outboard side of piston 16 to rotate propeller blades 13 toward high pitch and feather position. As soon as the position is reached, mechanical stops, not shown, in well known manner halt the blades and cause the pressure in the governor to build up to a predetermined value, at which the pressure switch 34 is adapted to cut out and break the circuit there through. This results in de-energization of. hold-in coil 148 of switch 138 and actuator 146 then returns to its neutral position whereby the pump 26 stops and the feathering operation is completed.

To unfeather propeller 11 the actuator 146 is manually moved in the reverse direction to cause movable contact to bridge contacts 141a, 142a, 143a, and 144a. With the bridging of these ontacts, current flows through contact 141a of push-pu switch 138, coil 153 of double pole relay 139 is energized by completion of a ground movable switch arm 157 of propeller ground switch 38 which is engaged with contact 156 of this ground switch 38, it being noted that at this time propeller 11 will be feathered and roller will be resting at approximately 184 on cam ring 37. In addition, arms 151 and 152 of double pole relay 139 move to circuit-making position to energize solenoid valve 33, providing a ground for this circuit through valve 33. Current through contact 143a of push-pull switch 138 energizes coil 166 of pump relay 35 to thereby start pump motor 27. Fluid will then flow from pump 26 through governor 21 to the inboard side of piston 16 to rotate propeller blades 13 to assume a low pitch angle. As soon as the blades 13 begin to windmill in the airstream of the aircraft the operator releases actuator 146 to break the circuit to coil 166 of relay 35, deenergizing coil 166 and inactivating pump 26.

In the event the operator inadvertently and erroneously holds actuator 146 in the reverse or out direction too long and continues to hold it there, the blades 13 will not continue on toward a reverse pitch, but rather will be caused to move back to feather position by virtue of roller 169 rolling onto a feathering cam 185 of cam ring 37 to thereby disengage switch arm 157 and contact 156 of ground switch 38 whereby the circuit to ground is cut 011 and relay 139 effects inactivation of solenoid valve 33. It is evident that as soon as actuator 146 is released pump 26 will be inactivated and if the propeller blades 13 are at a blade angle less than full feather so that windmilling of propeller 11 occurs, the governor 21 will then bring the propeller blades 13 to their normal operating position.

Propeller reversing and unreversing operations will now be described. Assuming the propeller 11 to be functioning in normal or low pitch condition, the propeller reversing control switch 39 will have its operating parts disposed in the positions best illustrated in Figs. 1, 2, 3, and 8. As seen, actuating assembly 85 will be in its upper position, as will be the movable contact members 71, 75 and 79 of switch units 66, 67, and 76.

When it is desired to reverse propeller 11 the throttle control lever 47 is operated to move cam surface 48 upon roller 94 to thereby pivot actuating arms 86 and 87 toward the top of housing 49 of reversing control switch 39. This movement of arms 86 and 87 depresses operating pins 81, 82 and 83 of switch units 66, 76, and 67, respectively, to thereby bring movable contact members 71 and 79 of units 66 and 76 into engagement with contacts 69 and 78, respectively, and to also bring movable contact member 75 of unit 67 into engagement with contacts 73 and 74 thereof, as best illustrated in Fig. 9. As previously described, the pin actuator assemblies 93, 92 and 93 are adjusted so that pin 33 of unit 67 is the last of the group of pins 31, S2 and 83 to be depressed whereby movable contact member 75' of unit 67 engages contacts 73 and 74 after the movable contact members 71 and 79 and the contacts of units 66 and 76 have engaged their respective contacts 69 and 73. With this sequencing, the current to reversing co; iol s" tch 32 coming through movable contact member 75 cannot cause arcing across the contacts of switch units and 7-6 since those contacts have already been made, and thereby the operating life of such contacts is increased.

Reference will now be had to Fig. 12 to dcsc b 2 results of the completed circuits in switch units do. 37

and 76 arising from the depression of their operatinpins 81, 83 and 82, respectively.

As hereinbefore stated, power from battery 41 is supplied to control switch 39 through member 75 and contacts 73 and 74 of switch unit 67. This power passes from contacts 73 through lead 175 to thereby energize coil 166 of pump relay 35, closing the circuit to motor 27 and starting operation of pump 26.

Current also passes from contact 74 of unit 67, through lead 1'76, through movable contact member "if. of switch unit 6i? and through contact 69 thereof from which it passes through contact 173 and switch arm 152 of double pole relay 139 to solenoid valve From solenoid valve 33 the circuit is completed to ground through movable contact member 79 and contact 73 of switch unit 76 when the latter has been actuated by its associated actuator pin assembly 91 whereby solenoid valve 33 is energized. With solenoid valve 33 energized and pump 26 directing a flow of oil through the governor .21 and through line 22 to cylinder 17 at the rear of piston 16 rotation of the propeller blades 13 into reverse angle position is effected. Since it necessitates a volitional act of the operator to move the throttle control lever 47 to obtain movement of actuator pin assembly )1 to secure the positive engagement of contact 73 with member 79, and since engagement of contact 7% with member '79 is required to energize solenoid valve 3., protection is afforded against inadvertent or accidental energization of the solenoid valve 33 and consequent reversing of propeller 11 without first having an operation of reversing switch 3i". More specifically, accidental energization or actuation of solenoid valve 33 beyond the control of the operator can be had only if there is both a short circuit of lead 177, which supplies power to solenoid valve 33, across a power lead from battery 41, and a short circuit of lead 179 to ground. That the latter two conditions will ever arise is extremely remote. It may, therefore, be stated that a deliberate act of the operator must be had before propeller 11 will reverse.

At the end of the reversing operation, the pressure of incoming oil to cylinder 37 does not continue to build up but is maintained at the required magnitude through a relief valve (not shown) in pump 2-6, in a manner well known to those skilled in the art. Pump 26 continues to run and solenoid valve 33 remains energized this time, thereby serving to hold the propeller 11 in its reversed position.

To unreverse propeller 11 and return it to normal position the throttle control lever 47 is operated to disengage camming surface 43 from roller 94 on actuating assembly 85. This permits actuating arms 86 and S7 of control switch 39 to move upwardly under the bias of their respectively associated springs 108 and 109. In this movement of arms 86 and 37, pins 31, 82 and 83 of switch units 66, 76, and 67, respectively, are disen gaged by pin actuator assemblies 93, 91 and 92, respectively, whereby movable contact members 71 and 79 of switch units 66 and 76 disengage their cooperating contacts 69 and 78 and return to their normally engaged position upon the opposed contacts 68 and 77, respectively, as best illustrated in Fig. 10. This results in the breaking of the circuit to solenoid valve 33.

it is to be noted that movable contact member 75, as previously described, remains engaged with contacts 73 and 74 of switch unit 67 until unreversing is completed, as will be seen, whereby pump 26 remains running. With pump 26 running and solenoid valve 33 deenergized a how of oil will then be routed by the governor 21 through line 23 to c linder 17 to the outboard side of piston 16. Piston 16 moves to rotate propeller blades 13 into positive normal thrust angle. When the propeller blades 13 reach positive pitch, roller 160 of blade ground switch off reversing cam 186 thereby causing engagement or movable switch arm 157 and Contact 156 of ground switch 33, and completing the circuit from battery 41, across movable contact 75 and contact 74 of switch unit 67, through solenoid 121 to ground. This results in the energization of solenoid 121 which in turn causes the upward movement of movable core 125 of solenoid 121. Core 125 in its upward movement strikes pin 34 of switch unit 67 thereby effecting disengagement of movable contact 75' and contact 73 of switch unit 67 as illustrated in Fig. 11 whereby the circuit through lead 1 5 to pump relay 35 is cut and pump 26 is inactivated. It is apparent that disengagement of movable contact 75 and contact 74 also deenergizes solenoid 121 and con trol switch 39 and the system are thus returned to normal condition.

While certain preferred embodiments of the invention have been specifically disclosed, it is understood that the invention is not limited thereto as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation within the terms of the following claims.

I claim:

1. A propeller reversing control switch comprising a plurality of electrical switches, each of said switches including an operating pin and one of said switches including a reset pin, actuating means operable for actuating said pins to effect circuit making operation of said switches, and resetting means operable for actuating said reset pin to return said one of said switches from circuit making to circuit breaking position, said resetting means comprising a solenoid having an armature movable to actuate said reset pin.

2. An electrical switching mechanism comprising first and second electrical switches, each of said switches including contact means movable between circuit open and circuit closed position and which are biased for movement automatically into circuit open position, and each of said switches including an operating pin for actuation of said contact means to circuit ciosed position, a third electrical switch, said latter switch including contact means movable between circuit open and circuit closed position, an operating pin for actuation of said contact means from circuit open to circuit closed position and a reset pin actuable for returning said contact means to circuit open position, means movable to actuate said operating pins to move said contact means of said first, second, and third electrical switches to circuit closed position, and means separate from and adapted to actuate said reset pin to move said contact means of said third electrical switch to circuit open position.

3. An electrical switching mechanism comprising a housing, a plurality of electrical switches supported in said housing, lever means movably mounted to said housing and operatively associated with each of said electrical switches, said lever means being actuable to operative position to effect circuit making operation of said electrical switches, a reset pin associated with at least one of said plurality of switches and actuable for effecting circuit breaking operation thereof, the remainder of said electrical switches being constructed and arranged to automatically perform a circuit-breaking operation when said lever means is moved to inoperative position, spring means associated with said lever means for moving said lever means to inoperative position, and an electro-magnet mounted within said housing, said electromagnet including an armature movable for actuating said reset pin.

4. An electrical switching mechanism comprising a housing, first and second self-contained electrical switches supported in said housing, each of said switches including contact means movable between circuit open and circuit closed position and which are biased for movement automatically into circuit open position, and each of said switches including an operating pin actuable for movement of said contact means to circuit closed position, a third self-contained electrical switch in said housing, said latter switch including contact means movable between circuit open and circuit closed position, an operating pin actuable for movement of said contact means from circuit open to circuti closed position and a reset pin actuable for returning said contact means to circuit open position, lever means movably mounted on said housing, a plurality of adjustable actuator pin elements carried by said lever means, one provided for each of said operating pins of said first, second, and third electrical switches for open ativc engagement therewith, said lever means being actuable for movement to operative position to move said actuator pin elements to actuate said operating pins, spring means operatively associated with said lever means for automatic return thereof to inoperative position to permit said movable contact means of said first and second electrical switches to move automatically from circuit closed to circuit open position, and means separate from and adapted to actuate said reset pin to move said contact means of said third electrical switch to circuit open position.

5. An electrical switching mechanism comprising a housing, first and second self-contained electrical switches supported in said housing, each of said switches including contact means movable between circuit open and circuit closed position and which are biased for movement automatically into circuit open position, and each of said switches including an operating pin actuable for movement of said contact means to circuit closed position, a third self-contained electrical switch in said housing, said latter switch including contact means movable between circuit open and circuit closed position, an operating pin actuable for movement of said contact means from circuit open to circuit closed position and a reset pin actuable for returning said contact means to circuit open position, lever means movably mounted on said housing, a plurality of adjustable actuator pin elements carried by said lever means, one provided for each of said operating pins of said first, second, and third electrical switches for operative engagement therewith, said lever means being actuable for movement to operative position to move said actuator pin elements to actuate said operating pins, spring means operatively associated with said lever means for automatic return thereof to inoperative position to permit said movable contact means of said first and second electrical switches to move automatically from circuit closed to circuit open position, and an electromagnet supported in said housing and having an armature movable to actuate said reset pin to move said contact means or said third electrical switch to circuit open position.

6. An electrical circuit controlling instrumentality comprising a plurality of at least three electrical switching means, each having an operating element movable between circuit-closing and circuit-opening positions, the operating element of at least one of said switching means being biased to circuit-opening position when in said circuit-opening position and to circuit-closing position when in said circuit-closing position, the operating elements of the others of said plurality of switching means each being biased to a circuit-opening position, a common actuating means operatively associated with said plurality of switching means for overcoming the bias on said operating elements of said plurality of switching means to move all of said operating elements positively to circuit-closing positions, reset means embodying a movable element operable to move positively said operating element of said one of said switching means to a circuit-opening position, and electro-magnetic means for operating said movable element of said reset means.

References Cited in the file of this patent UNITED STATES PATENTS 1,703,056 Brockway Feb. 19, 1929 2,338,365 Thorp et al. Ian. 4, 1944 2,349,647 Boisseau et al May 23, 1944 2,511,271 Kaminky et al June 13, 1950 2,541,314 Weber et al Feb. 13, 1951 2,579,172 BOrclelOn Dec. 18, 1951 FOREIGN PATENTS 917,249 France Sept. 9, 1946 

